The present invention relates generally to integrated circuits. More particularly, the invention relates to a method and circuitry for hot-swap protection circuits.
A hot swap operation is an insertion action or a removal action of a device while the system using it is receiving power, coupling the power from the system to the device. Such an operation can cause external capacitors to draw currents high enough to disturb system operations or even cause permanent damage to either or both the device and the system.
Hot-swap protection circuits enable electronic circuits to be connected to each other and disconnected from each other while powered. Hot-swap protection circuits are required in many applications where it is not practical to shut down an electronic system while replacing or adding circuit boards to it. Such protection circuits, or systems, are used in telephone switching hubs, corporate network server hubs, and in laptop or desktop computers with PCMCIA connectors. All of the examples require connection or disconnection under power and so on.
Conventional hot-swap protection circuits employ connectors with at least one set of sensor pins, which are a set of extra long and extra short pins, connected to voltage detectors. These sensor pins allow immediate detection of connection and/or disconnection by sensing the presence and/or absence of the applied voltage. It is well known that a single set of sensor pins—whether at the top, middle, or bottom—might not be enough to detect a hot-swap event.
For the best reliability, it is often necessary to use two sets of sensor pins, one set at the top and one set at the bottom of a hot-swappable card. Adding additional sets of sensor pins increase reliability, but increases costs to the overall system. Additionally, conventional hot-swap protection systems using sensor pins do not always detect the application or removal of power to a system.